PURPOSE MRI proton density fat fraction (PDFF) can be calculated using magnitude (MRI-M) or complex (MRI-C) MRI data. The purpose of this study was to identify, assess, and compare the accuracy of common PDFF thresholds for MRI-M and MRI-C for assessing hepatic steatosis in patients with obesity, using histology as reference. METHODS This two-center prospective study included patients undergoing MRI-C- and MRI-M-PDFF estimations within 3 days before weight loss surgery. Liver biopsy was performed, and histology-determined steatosis grades were used as reference standard. Using receiver operating characteristics (ROC) analysis on data pooled from both methods, single common thresholds for diagnosing and differentiating none or mild (0-1) from moderate to severe steatosis (2-3) were selected as the ones achieving the highest sensitivity while providing at least 90% specificity. Selection methods were cross-validated. Performances were compared using McNemar's tests. RESULTS Of 81 included patients, 54 (67%) had steatosis. The common PDFF threshold for diagnosing steatosis was 5.4%, which provided a cross-validated 0.88 (95% CI 0.77-0.95) sensitivity and 0.92 (0.75-0.99) specificity for MRI-M and 0.87 sensitivity (0.75-0.94) with 0.81 (0.61-0.93) specificity for MRI-C. The common PDFF threshold to differentiate steatosis grades 0-1 from 2 to 3 was 14.7%, which provided cross-validated 0.86 (95% CI 0.59-0.98) sensitivity and 0.95 (0.87-0.99) specificity for MRI-M and 0.93 sensitivity (0.68-0.99) with 0.97(0.89-0.99) specificity for MRI-C. CONCLUSION If independently validated, diagnostic thresholds of 5.4% and 14.7% could be adopted for both techniques for detecting and differentiating none to mild from moderate to severe steatosis, respectively, with high diagnostic accuracy.

中文翻译：

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用于评估肥胖患者肝脏脂肪变性的基于幅度和复杂度的化学位移编码 MRI 的常见质子密度脂肪分数阈值的准确性。

目的 MRI 质子密度脂肪分数 (PDFF) 可以使用幅度 (MRI-M) 或复杂 (MRI-C) MRI 数据进行计算。本研究的目的是识别、评估和比较 MRI-M 和 MRI-C 的常见 PDFF 阈值在评估肥胖患者肝脏脂肪变性时的准确性，使用组织学作为参考。方法这项两中心前瞻性研究包括在减肥手术前 3 天内接受 MRI-C- 和 MRI-M-PDFF 估计的患者。进行肝活检，组织学确定的脂肪变性分级用作参考标准。对两种方法汇集的数据使用接受者操作特征 (ROC) 分析，选择用于诊断和区分无或轻度 (0-1) 中度至重度脂肪变性 (2-3) 的单一通用阈值作为实现最高灵敏度同时提供至少 90% 特异性的阈值。选择方法经过交叉验证。使用 McNemar 的测试比较了性能。结果 在纳入的 81 名患者中，54 名 (67%) 患有脂肪变性。诊断脂肪变性的常见 PDFF 阈值为 5.4%，交叉验证的 MRI-M 敏感性为 0.88（95% CI 0.77-0.95），特异性为 0.92（0.75-0.99），敏感性为 0.87（0.75-0.914），0.81（0.75-0.91）。 0.61-0.93) MRI-C 的特异性。区分脂肪变性 0-1 级和 2 到 3 级的常见 PDFF 阈值为 14.7%，交叉验证的 MRI-M 敏感性为 0.86（95% CI 0.59-0.98），特异性为 0.95（0.87-0.99），敏感性为 0.93（ 0.68-0。99) 对 MRI-C 的特异性为 0.97(0.89-0.99)。结论 如果独立验证，可采用 5.4% 和 14.7% 的诊断阈值分别用于检测和区分无、轻度、中度到重度脂肪变性的两种技术，具有很高的诊断准确性。